Experimental Study on Small-Strain Shear Modulus of Unsaturated Silty-Fine Sand
Round 1
Reviewer 1 Report
In the manuscript, the small-strain shear modulus of unsaturated sand was investigated by developing a combined bending element-resonant column(BE-RC) test system. The test results indicated that the value of the shear modulus of sand reaches the maximum value near the optimum saturation under the same shear strain condition. The prediction model of the maximum shear modulus of unsaturated sand was improved to achieve continuity at the optimum saturation, and the variation of shear modulus with saturation in three stages was explained based on the morphological evolution of intergranular water in grains and the mechanism of capillary action. The study investigated the variation of shear modulus with saturation and the research is interesting. However, before recommending its publication in Applied Science. A re-submission addressing the suggestions below is recommended.
(1) In Table 4, the corresponding matrix suction is not proposed when the saturation value is zero, but the maximum shear modulus value for specimen saturation of zero appears in Fig. 10. Please explain whether the specimen with zero saturation is the same specimen as other specimens with different saturation.
(2) “Although the distance between particles tends to be minimized and the interparticle short-range force could work, the distance between particles is still too large for sand particles which are beyond the action range of the interparticle short-range force [28-29].”. Please explain the specific range of action of van der Waals forces and electrostatic gravitational forces in the short-range action.
(3) “The above equation (Eq.7) overcomes the problem of discontinuity in predicting the maximum shear modulus Gmax of soils with different saturations at the optimum saturation by Eq.3.” The “Eq.3” should be modified to “Eq.4”. Some symbols should be italic, please check this manuscript thoroughly.
(4) The omission of fluent English with the right grammar and some long sentences made the manuscript hard to follow. A detailed text proofreading needs to be done before a potential resubmission.
Author Response
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Reviewer 2 Report
The paper investigated the shear modulus of unsaturated soil within the full small strain range. This work first modifies the base of the Stokoe RC instrument and install the BE, making the device can measure the dynamic shear modulus of the same specimen in the whole small strain range (10-6~10-3) under the control of atrix suction. The reliability of the device was checked using combined test experiment of BE-RC for unsaturated sand in the dehydration path. The effect of saturation on the small-strain shear modulus of sand was the discussed.
On the whole, the topic of this manuscript is both academic and practical interesting. However, the reviewer thinks the presentation of this manuscript should be improved (more explanation should be added) and the written English of the manuscript needs to be polished before the publication.
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Reviewer 3 Report
Dear Authors, The paper presents the development of the BE-RC test device and presents the lab testing results for small strain G of unsaturated silty fine sand. It is an interesting topic to discuss the problem from a Geotechnical point of view. However, it is believed, that the paper needs to detail various sections of the article body in terms of the research discussion and concept clarity. The Review comments are included in the manuscript as an uploaded, annotated, PDF copy of this paper.
Comments for author File: 
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Reviewer 4 Report
The author has made a good attempt to understand the " Experimental Study on Small Strain Shear Modulus of Unsaturated Sand". However, he fails to address the few comments.
The details are mentioned below:
1. Objective should be refined effectively.
2. Existing kinds of literature are missing.
3. Introduction to bending element-resonant column must be elaborate in detail.
4. Sample preparation details are missing
5. Figure 8 discussion is limited. The detailed interpretation must be carried out.
6. You have not conducted a low strain level test on how you can plot G/Gmax vs strain. How you have taken the G value
7. There is a lack of mechanism of decay of dynamic shear modulus in sand details that are missing.
8. This type of research work is already published in articles, so this article is unique from others.
9. Conclusion should be rewritten
Author Response
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Round 2
Reviewer 3 Report
Dear Authors, Thank you for the detailed and complted responces to my comments. I believe there are still multiple minor improvements required with the current manuscript. You can find my comments in the manuscript as an uploaded, annotated, PDF copy of this paper.
Comments for author File: Comments.pdf
Author Response
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